There are known many different tools and devices for drilling oil, gas, and water wells. A traditional device is usually composed of a bore string consisting of a plurality of tubular pipes driven by a power unit typically located on the surface. The power unit provides rotation of the pipes in turn revolving a drill bit that actually performs the drilling. Typically, lubrication of such drill bits is provided during the assembling process at manufacturer's facilities. In practice this lubrication is insufficient for durable exploitation of the bits that leads to their overheating and failure, and consequently to changing the bit for a new one that is very costly.
There have been proposed some devices to improve lubrication of the bits. An example of such drill bit is taught in U.S. Pat. No. 4,381,824: “In a non-sealed rolling cutter drill bit having at least one bearing journal shaft and a rolling cutter rotatably mounted on the shaft and having at least one flat interior end face in rotary bearing contact with the end of said bearing journal shaft to support end thrust loads, the improvement comprising: at least one lubricant rod slidably mounted in said shaft for longitudinal movement therein and arranged to contact said flat interior end face of said rolling cutter; and, biasing means associated with said lubricating rod and arranged to urge said rod against said flat interior end face during rotation of said rolling cutter to lubricate the end thrust bearing surfaces thereof.”
A drawback of such a device is that the lubricant rod relatively quickly wears out, and the bit continues rotation essentially without lubrication. This involves either failure, or destruction of the bit, or significant expenses for frequent replacements of the lubricant rod.